In recent years, in order to substantially widen a cover area of a radio base station or to maintain an electric field strength of received signals at a communication terminal, a technology in which a radio relay station connected to a radio base station is provided and the radio relay station is caused to relay communications between the radio base station and a communication terminal has been considered.
FIG. 21 is a diagram illustrating one form of a common radio communication system provided with a relay apparatus.
The radio communication system illustrated in FIG. 21 is composed of DeNBs (Donor evolved Node Bs) 1000-1 and 1000-2 that are radio base stations, an RN (Relay Node) 2000 that is a radio relay station, and UEs (User Equipments) 3000-1 and 3000-2 that are communication terminals.
The RN 2000 relays communication between the DeNB 1000-1 and the UE 3000-1.
Furthermore, the RN 2000 relays communication between the DeNB 1000-2 and the UE 3000-2.
Furthermore, a technology in which, when, in a radio relay station as described above, a downlink line control signal is sent from a radio base station to the radio relay station at a timing at which the radio relay station is sending a downlink line control signal to a communication terminal, the radio relay station allocates a resource region that can receive the downlink line control signal sent from the radio base station has been considered (refer to, e.g., PTL 1).